Why we can not overload the static_cast operator?

[=?utf-8?B?5Zyw55CD5Y+R5Yqo5py6?=]

In C++ we can not overload the explicit typecast operator like
static_cast, dynamic_cast, const_cast and reinterpret_cast. The only
we can do is the implicit typecast operator like operator
MyClass::MyDistType().

I agree there are maybe no meaning to overload dynamic_cast/const_cast/
reinterpret_cast, except the static_cast. If we enable the overloading
of static_cast, we could be able to force the user doing type casting
explicitly.

There are two ways to implemation this:

Suggestion 1:

class B;
class A
{
public:
friend B operator static_cast<B>(const A &);
};

A a;
// B b=a; //Error, no type casting operator
B b=static_cast<B>(a); //Pass, using the friend casting operator

Suggestion 2:

class B;
class A
{
public:
explicit operator B();
};

A a;
// B b=a; //Error, the type casting operator decalred as explicit
B b=static_cast<B>(a) //Pass, using explicit type casting

[Victor Bazarov]

????? wrote:

In C++ we can not overload the explicit typecast operator like
static_cast, dynamic_cast, const_cast and reinterpret_cast. The only
we can do is the implicit typecast operator like operator
MyClass::MyDistType().

I agree there are maybe no meaning to overload
dynamic_cast/const_cast/ reinterpret_cast, except the static_cast. If
we enable the overloading of static_cast, we could be able to force
the user doing type casting explicitly.

There are two ways to implemation this:

Suggestion 1:

class B;
class A
{
public:
friend B operator static_cast<B>(const A &);
};

A a;
// B b=a; //Error, no type casting operator
B b=static_cast<B>(a); //Pass, using the friend casting operator

Suggestion 2:

class B;
class A
{
public:
explicit operator B();
};

A a;
// B b=a; //Error, the type casting operator decalred as explicit
B b=static_cast<B>(a) //Pass, using explicit type casting

I think that has been discussed a couple of times in the past.
In fact, I vaguely remember that there was a valid reason not to
allow 'explicit' with the type conversion function. But I don't
recall what it was.

Try looking on 'groups.google.com'. You should find something.

V
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